Activated ras oncogenes promote growth arrest and accumulation of cholesterol esters and other neutral lipids when expressed in REF52 and in A7r5 and AlO smooth muscle cells. Adenovirus ElA and SV4O large T antigen enable ras oncogenes to transform these cell types and protect from ras-induced growth arrest and lipogenesis. proposed experiments will study the biochemical functions of ras, ElA, and SV40 large T antigen; regulation of cellular responses to ras; and mechanisms involved in multistep carcinogenesis and, possibly, the etiology of atherosclerosis. In particular, the proposed experiments will: (1) investigate signal transduction pathways to understand how growth responses to mitogenic stimuli are blocked by ras and how viral oncogenes circumvent cellular requirements for mitogenic stimuli; (2) isolate untransformed lines expressing activated Ha-ras. Ki-ras 4A and 4B and N-ras P21s to compare ras P21s for different effects on growth factor responses in the absence of secondary changes caused by transformation; (3) determine if resistance of REF52. A7r5 and AlO cells to transformation by ras is dominant in cell fusions; (4) select for mutant cells able to tolerate ras and analyse the mechanisms of tolerance; (5) determine the source and identity of each lipid species induced to accumulate by ras; (6) assess whether specific lipases are activated by ras in vivo and in cell-free extracts, comparing normal and ras tolerant cells; (7) test whether biochemical defects observed in cell free extracts from ras tolerant mutants are complimented by proteins from normal cell- extracts; (8) investigate possible interactions between ras p21 and cellular proteins by direct binding in vitro and by competition between P21s in vivo: (9) determine the extent to which cellular gene expression is regulated by ras and collaborating oncogenes. by two-dimensional gel electrophoresis; (10) clone differentially expressed genes by cDNA subtraction, with particular emphasis on isolating genes whose expression is affected in opposite ways by ras and ElA; and (11) study repression of the aortic smooth muscle alpha-actin gene by ras transformation.